Flow Drilling Fastener Geometry for Lower Thread Forming Torque

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Solution Overview

Problem

Existing hole forming self-tapping screws face challenges when used in thick or strong materials, as the thread forming torque can exceed the torsional strength of the fastener, leading to failure, due to excessive material flow and friction forces.

Innovation Solution

A self-tapping flow drilling screw with a helical thread shank and a flow drilling tip of specific diameter proportions, where the tip diameter is greater than the minor diameter of the helical thread but less than or equal to the major diameter, allowing for optimized material flow and reduced friction forces, enabling effective use in thicker substrates without torsional failure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the fastener uses a conventional forming tip with constant diameter smaller than pitch diameter, then the fastener can be manufactured with standard geometry, but the hole created is too small causing excessive material flow into threads, excessive friction forces, and high thread forming torque that exceeds torsional strength in thick materials

Engineering Contradiction:

Improvetorsional strengthVSAvoidthread forming torque

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by modifying the forming tip diameter to be greater than the pitch diameter of the threaded portion, which is a fundamental departure from conventional geometry. This parameter change creates a larger initial hole that reduces material flow into the threads during thread forming, thereby reducing friction forces and thread forming torque, preventing fastener failure in thick or strong materials

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by creating a zone of differentiated geometry where the forming tip has a different diameter characteristic than the threaded portion. The forming tip diameter is specifically designed to be greater than the pitch diameter, creating a localized region that facilitates reduced material flow and friction, while the threaded portion maintains its standard geometry for thread formation

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the fastener uses a forming tip with diameter greater than minor diameter but less than or equal to major diameter of helical thread, then material flow is optimized and friction forces are reduced, but the fastener geometry becomes more complex to manufacture

Engineering Contradiction:

Improvefriction forcesVSAvoidfastener geometry

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent applies parameter changes by defining specific diameter relationships for the forming tip relative to the helical thread dimensions (greater than minor diameter, less than or equal to major diameter). This parameter specification optimizes material flow and reduces friction forces while maintaining manufacturability through clear geometric definitions that can be implemented using standard manufacturing processes

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If the fastener uses a forming tip with constantly reducing cross section towards terminating portion, then the tip can penetrate the substrate, but no optimization is provided for material flow resulting in excessive friction forces and high thread forming torque

Engineering Contradiction:

Improvepenetration capabilityVSAvoidthread forming torque

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by specifying that the forming tip diameter at its largest point should be greater than the smallest diameter of the helical thread feature. This parameter change maintains the penetration capability through the substrate while simultaneously optimizing material flow during thread forming, reducing friction forces and thread forming torque compared to constantly reducing cross-section tips

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution allows for effective fastening in materials up to 10 mm thick, such as aluminum, and 4-8 mm thick magnesium, by reducing thread forming torque and friction forces, preventing fastener failure and ensuring secure connections.

Implementation Method 1

hole forming self-tapping screws fasten multiple materials together by using frictional heat generated by rotation and axial loading of the fastener against the substrate materials

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

The heat plasticizes the material allowing the fastener to penetrate through the substrates without cutting

Methodology Applied

Scientific EffectHeat: Heating

Data Source

PatentUS20230129583A1Torque reducing flow drilling fastener for thick materials and method of using such fastener

Publication Date: 2023.04.27 SEMBLEX CORP

AI summary

A self-penetrating thread forming and flow drilling fastener for thick materials with a generally cylindrical partially threaded shank, a drive system at the first end of the shank and a flow drilling tip at the second end of the shank. The flow drilling tip is sized larger than the minor diameter of the threaded shank but less than the major diameter to control installation torque enabling installation into thick materials with greatly reduced risk of torsional failure resultant from a decrease in torque. The flow drilling tip and threads may be a variety of shapes or thread types based on the substrate material the fastener is installed into.